HOW FAST? 0.0 / 5 ? ChemistryRatesA2/A-levelOCR Created by: upsidedown1004Created on: 21-06-16 13:06 Define rate of reaction change in concentration of reactants/ products per unit time 1 of 20 What is meant by the initial rate? rate at start where gradient steepest 2 of 20 How can rate be measured? Acids/bases - Change in pH with pH probe/ titrations// gas vol produced per unit time/ rat elf colour change 3 of 20 Define the rate equation illustrates relationship between rate of reaction and initial concentration of reactants 4 of 20 What is the rate equation? r = k [A]m [B]n 5 of 20 What is k? rate constant, constant that links rate of reaction with the conc of reactants raised to the power of their order 6 of 20 What is the order of a reaction? power to which the conc of reactants are raised to in the rate equation 7 of 20 describe a zero order conc vs time graph straight line, half life decreases 8 of 20 describe a first order conc vs time graph curve, constant half life - half life independent of the change in conc 9 of 20 describe a second order conc vs time graph curve, half life increases 10 of 20 Define half life the time taken for the concentration of reactants in a reaction to decrease by half 11 of 20 What is the rate determining step? the slowest stop in a reaction mechanism which determines the overall rate of reaction 12 of 20 describe a zero order rate vs conc graph conc does not affect rate, straight horizontal line 13 of 20 describe a firs order rate vs conc graph straight line through origin, conc is directly prop to rate 14 of 20 describe a second order rate vs conc graph rate is prop to change in conc-.squared / curved positive line 15 of 20 How does temperature effect k? rate of reaction will always increase at higher temps, cause k to increase 16 of 20 Describe the effect temperature has on k using a Maxy B distribution graph more molecules all have energy greater than or equal to activation / more successful collisions/ exponential relationship 17 of 20 Describe the rate determining step reactants involved in the RDS are present in the rate equation/ any step that occurs after will not affect rate/ can be predicted/ use to find order 18 of 20 what is an intermediate species? of a multistep reaction, a molecule/ ions generated in one step as a product but used win another as a reactant 19 of 20 What evidence would there be that a reaction takes place in more than one step? elements in chemical equation that are not in the rate equation/ orders in rate reaction differ to those in the chemical equation 20 of 20
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